Electromagnetic induction-type protective relay having improved adjustment means



Aug. 1, 1967 P. KOTOS 3,334,321 ELECTROMAGNETIC INDUCTION-TYPE PROTECTIVE RELAY HAVING IMPROVED ADJUSTMENT MEANS Filed Oct. 4, 1965 3 Sheets-Sheet 1 we /NVEN ran:

PETER Ko 70 6 ATTORNEY Aug. 1, 1967 P. KOTOS 3,334,321 ELECTROMAGNETIC INDUCTION-TYPE PROTECTIVE RELAY HAVING IMPROVED ADJUSTMENT MEANS Filed Oct. 4, 1965 5 Sheets-Sheet 2 0 a; I O /2 36 Q /NVENTOR.' PETER K0705,

BY QiktiW ATTORNEY Aug. 1, 1967 o os 3,334,321

ELECTROMAGNETIC INDUCTION-TYPE PROT'CTIVE RELAY ROVED ADJUSTMENT MEANS HAVING I MP Filed Oct. 4, 1965 INVENTOR. PETER KoTos,

ATTORNEY United States, Patent 3,334,321 ELECTROMAGNETIC INDUCTION-TYPE PROTEC.

TIVE RELAY HAVING IMPROVED ADJ UST- MENT MEANS Peter Kotos, Drexel Hill, Pa., assignor to General Electric Company, a corporation of New York Filed Oct. 4, 1965, Ser. No. 492,548 6 Claims. (Cl. 335177) This invention relates to electromagnetic relays, and more particularly it relates to improved means for conveniently adjusting certain mechanical parts of inductiontype protective relays.

Induction-type relays are used in the art of protective relaying to perform appropriate circuit controlling func tions in response to predetermined abnormal or fault conditions occurring in an electric power system or utilization apparatus that is being protected. Occurrence of an abnormal condition is reflected by critical changes in the magnitude of or relationships between system current and voltage. By using such characteristic system quantities to energize the relay windings, the torque acting on the movable armature of the relay can be made responsive to their magnitude and phase relationships, and the relay can be designed to pick up at precisely the critical point desired.

My invention is particularly concerned with inductioncup or induction-cylinder relays. For a general understanding of conventional construction, operating principles, and practical applications of a typical prior art relay of this kind, see the paper written by R. M. Hutchinson, The Mho Distance Relay, 65 Transactions of the American Institute of Electrical Engineers 353 (June 1946). Although such relays have had a long and successful history, they also have had some recognized shortcomings. Their complexity and manufacturing costs have been undesirably high. Furthermore, it has been relatively inconvenient to manipulate certain mechanical adjustment means with which they are conventionally provided. In the latter regard, it has sometimes been necessary to partially disassemble the relay in order to finally adjust its magnetic structure as required.

Accordingly, it is a general object of my invention to provide an improved induction-type protective relay characterized by simpler construction and adjustments than has heretofore been obtained.

Another object is to provide improved adjustment means in such a relay for the purpose of increasing the ease and convenience of precisely adjusting the relay without adversely affecting its operation or its manufacturing costs.

In carrying out my invention in one form, I provide an electromagnetic relay comprising a frame or stator that includes a plurality of salient poles projecting symmetrically toward a central axis. A co-axial magnetizable core is spaced apart from the pole faces to define therewith a plurality of gaps, and a current conducting armature is disposed for movement through these gaps. A plurality of magnetic flux producing coils are arranged on the stator to establish in said gaps magnetic fields which interact in the armature to produce a driving torque therein.

In one aspect of my invention, at least one peripheral portion of the aforesaid core is relatively flat, and the core is rotatably mounted on a supporting member so that the angular location of its flat portion can be changed as required for proper relay operation. According to my invention, the core includes an appendage that is resiliently clamped to the supporting member, and an adjusting element is keyed to the core for joint rotation therewith about its aXis. By applying an external force to a conveniently accessible peripheral portion of the latter element, the core can be rotated and the angular position of its flat portion precisely ad usted.

3,334,321 Patented Aug. 1, 1967 In another aspect of the invention, movable circuit controlling means is coupled to the aforesaid armature which, upon operation of the relay, drives the circuit these fingers and the body, whereby the ring can be rotated to ad ust the deflection of the control spring by applying an external force to its peripheral portion.

the accompanying drawing in which:

' FIG. 1 is a top plan View of an electromagnetic inductron relay embodying my invention FIG. 1A is a reduced plan view inner core of the FIG. 1 relay in which the magnetic flux are more clearly shown;

FIG. 2 is a side elevational view, of the realy shown in FIG. 1;

FIG. 3 is an enlarged sectional view taken through lines 33 of FIG. 2;

partly broken away,

g four s mmetrrcally disposed salient poles y 11, 12, 13 and 14. The body of stator 10 forms a closed magnetic path or loop inwardly disposed concave pole faces. The front pole 13 and the back pole 11 are longer than the side poles 12 and 14 of the stator.

The stator 10 is mounted on top of a rigid supporting to external supporting Also mounted on the bracket 20 is a hollow cylindrical member or core 23 of laminated magnetizable matefor magnetic flux issuing from the faces of the respective poles.

I 4 a third coil having leads C is disposed on spool 36 in the case of the offset mho relay):

Desired Characteristic Coil Leads Energized in Accordance With-- An electroconductive armature or rotor 24 is mounted on a rotatable shaft 25 whose axis is coextensive with the axis of the core 23 which is on the centerline 19 of the stator 10. A portion of the surface of this current conducting induction element 24, which preferably is a light-weight, inverted cup-shaped member fitting loosely on the cylindrical core 23, extends into the gaps formed by the core 23 and the faces of the four stator poles 11 14 for movement in a direction generally parallel to the pole faces, and thus the current conducting path provided by the rotor lies substantially transverse to the magnetic fields between the core and the respective pole faces. The rotor 24 is actuatable in either direction by driving torque created by the interaction of the magnetic fields in the rotor. Rotation of the rotor in a clockwise direction, as illustrated in the drawings, carries a movable switch contact 26 into engagement with a cooperating stationary contact 27 thereby to perform a circuit controlling operation. The stationary'contact 27 is part of a stationary contact assembly 28 that is fastened to an insulating member 29 mounted on top of the stator 10 by means of a pair of long bolts 30. The construction and arrangement of the shaft 25, the contacts 26 and 27, and the related parts of my relay will hereinafter be described in greater detail.

As can be seen most clearly in FIG. 1A, various electrical coils or windings are disposed on the stator 10. These magnetic flux producing coils are wound on spools 3136 which embrace, respectively, the four sections 15- 18 of the stator body and the non-adjacent stator poles 11 and 13. In the illustrated relay there is a single multiturn coil on each of the spools 31-34, and its leads have been identified in FIG. 1A by the reference letter A. The respective leads A of the coils on the spools 31-34 are intended to be interconnected for energization by a common alternating electric input quantity, and these connections will be arranged so that magnetic flux proportional to this quantity is produced in the side poles 12 and 14 of the stator 10. A pair of coils having leads B and B are mounted on the spool 35, and another pair of coils having leads C and C are mounted on the spool 36, whereby a net magnetic flux proportional to the resultant of the alternating electric input quantities that energizes these leads is produced in the diametrically opposed poles 11 and 13.

The fluxes produced upon energization of the various relay coils establish magnetic fields in the four gaps formed between the pole faces to the stator 10 and the core 23. In a manner well known to those skilled in the art, the magnetic fields interact in the rotor 24 to create a driving torque for actuating the rotor. The net torque acting on the rotor may be in a clockwise or a counterclockwise direction. It will be assumed that positive or clockwise movement of the rotor 24 is required for relay operation. Whenever the net driving torque is positive, the relay operates to perform its preselected control function, and whenever the net driving torque is Zero or negative, no operation is obtained.

The operating characteristic of the relay will depend on the source of the input quantities selected to energize the illustrated coils. A wide variety of combinations is possible, as indicated by the following table (note that The key to the symbols used in this table is set forth below:

I is current in line 1 of the circuit being protected. 1 is current in line 2 of that circuit.

Z is a predetermined constant impedance.

E is line-to-line voltage of the protected circuit.

P is a polarizing quantity (either current or voltage). S is a shading coil.

An example of the external circuit connections used to obtain the operating characteristic of a reactance relay can be found in my copending patent application S.N. 492,484 filed concurrently herewith.

In a relay structure of the kind thus far described, a small amount of unsymmetrical leakage flux is inevitably present in the respective gaps. Principally this is due to the dimensional tolerances of the component parts of the magnetic circuit. As a result, spurious torques are introduced in the rotor 24 that tend to cause misoperation of the relay under certain input conditions. In order to counteract this effect and ensure proper relay operation, the periphery of the core 23 is deliberately provided with at least one relatively flat portion 23a. In FIG. 1A a symmetrical pair of flats 23a have been shown on the core 23, which configuration is preferable to a single fiat except in the offset mho relay. The flats can be moved by rotating the core to an angular location in which their afiect on magnetic dissymmetry will exactly counterbalance whatever inherent dissym'metry was present. The core is properly adjusted when it is in an angular position that results in there being positive torque on the rotor 24 for all operating conditions of the input quantities but no positive torque for any non-operating condition (especially, in the case of distance relays, when E is zero and I is maximum, or when I is zero and E is maximum, or when E and IZ have equal magnitudes).

The construction of my improved means for mounting the core 23 and for providing for convenient adjustment thereof is best shown in FIGS. 3 and 4 which will now be described. As can be seen in FIG. 3, the core 23 has intimately inserted therein a tubular metal bushing 41, preferably of brass. The bushing 41 has a flanged portion 41a below the core proper that bottoms on the supporting bracket 20, and an axial extension 41b of the bushing extends through a cooperating hole in the bracket where it is free to rotate. The lower end of the bushing extension 41b is provided with external screw threads 41c, and opposite sides of this end are flattened as is indicated at 41d in FIG. 4.

An adjusting element 42 is disposed on the bushing 41 of the core 23. This element preferably comprises a washer-like member having an octagonal periphery and a slotted opening conforming to the cross section of the fiat part of the bushing extension 41b, see FIG. 4. The element 42 embraces the bushing extension 41b, and consequently it is keyed to the core 23 for joint rotation therewith.

Resilient means comprising a spring washer 43 is disposed between the element 42 and the underside of the supporting bracket 20, and the element 42 is firmly clamped against this spring washer by means of a plain washer 44 and a nut 45 appended to the threaded end 410 of the bushing. Thus the bracket and the adjusting element 42 are resiliently sandwiched between the bushing flange 41a and the nut 45. This mounting arrangement holds the core 23 securely in place on the supporting bracket 20 yet permits convenient adjustment of the cores angular position as desired. As is clearly apparent in FIGS. 2 and 3, the octagonal periphery of the element 42 is externally accessible for rotational adjustment by using a wrench or other appropriate tool (not shown) to apply tangential force thereto. This one-step adjusting operation can be carried out from in front of the relay without any disassembling.

The bushing 41 of the core 23 is also used to support a lower jewel bearing 46 for the coaxial shaft on which the relay rotor 24 is mounted. As can be seen in FIG. 3, the bearing 46 is located on top of a floating plug 47 which is supported by a helical spring 48 in a cup-like insert 49 pressed axially into the bushing 41. A bolt 50 threaded into the lower end 410 captures the spring 48 and the plug 47 therein. The lower end of the shaft 25 is equipped with an axial pin 51 that extends through a side bearing in the insert 49 for seating in the bearing 46.

At the upper end of the shaft 25 another side bearing 52 receives a coaxial guide pin 53 carried by a bolt 54 which is tightened by a lock nut 55 to an internally threaded metal insert 56 located in a bridge 29a of the insulating member 29 of the relay.

Approximately midway between its ends the shaft 25 has a knurled portion 25a to which two metal bosses 57 and 58 are attached. As is shown in FIG. 3, the closed end 24a of the cup-shaped electroconductive rotor 24 of the relay is firmly secured between these bosses, whereby joint rotation of the rotor 24 and the shaft 25 is obtained. Desirable friction damping of this rotation is provided by a metal washer 59 that rests on top of the boss 57. A thin fiber washer 60 overlies the metal washer 59.

The movable switch contact 26 of the illustrated relay is coupled to the rotor 24 by means of an electroconductive switch arm 61 projecting radially from the rotor shaft 25. This coupling includes a spring loaded clutch between the switch arm 61 and the shaft 25. One end of the switch arm encircles a first insulating bushing 62 which is telescopically disposed on a second insulating bushing 63 engaging the boss 57 of the shaft 25. This end of the switch arm is sandwiched between a flanged portion of the bushing 62 and an overlying annular insulating ring 64 which is urged downwardly by a helical spring 65 held in compression by a washer 66 and a lock nut 67 connected to the shaft 25. Upon rotation of the shaft 25 the spring loaded clutch assembly 6267 will cause the switch arm 61 to rotate correspondingly until the switch arm is stopped by a reaction force exceeding the limited torque that the clutch can frictionally transmit to the arm without slipping.

The movable switch contact 26 is located at the distal end of the switch arm 61. As it is shown in FIG. I, this ment of the relay rotor which will drive the switch arm 61 in the same direction until the movable contact 26 reaches its closed position in engagement with the cooperating contact 27 of the stationary contact assembly 28 (see FIG. 6).

Clockwise movement of the switch arm 61 is yieldably opposed by a co-axial spiral control spring 73 whose innected to a depending part 75a of a rotatable adjusting ring 75. The ring 75 is part of my improved adjustment means, soon to be described, for controlling the stress on the control spring 73 when the movable switch contact of the bushing releasably 26 of the relay is in its normal position. This adjustment means and the control spring have good electrical conductivity, and external circuit connections can be made to the movable contact 26 by attaching a lead-in wire (not shown) to a radially disposed terminal 77a of the adjustment means. The external circuit connections for the stationary contact 27 can be made at a terminal post 74 which also serves to fasten the stationary contact assembly 28 to the insulating member 29, as best seen in FIG. 2-

If desired, a second stationary contact assembly could be used in lieu of the backstop 71. The control spring 73 can be adjusted, with the relay in a deenergized state, to normally bias the movable contact 26 into engagement with either one of the cooperating stationary members, or alternatively it can be arranged to normally position the movable contact at a neutral or midpoint therebetween.

My improved means for adjusting the control spring 73 is seen to include the ring 75, a spring washer 76 adjacent to the ring, and a stationary annular supporting body 77 adjacent to the washer. As is best seen in FIG. 3, this assembly of parts 7577 is located above the upper end of the shaft 25 in coaxial relationship therewith. Its stahas two diametrically opposite lobes 77b which are afiixed to the underside of the insulating bridge 29a by a pair of rivets 78. As is clearly shown in FIGS. 2 and 6, the aforesaid terminal 77a extends radially outwardly from the body 77.

The stationary body 77 of my adjustment means also has a plurality of rigid fingers 77c extending in an axial direction from its inner edge through the washer 76 and the ring 75 and bending back over the underside of the ring, as indicated in FIG. 3, whereby the washer and the ring are captured between the body 77 and the tips of its fingers 77c. Thus, a three-part unitary assembly is formed. The ring 75 is provided with a conveniently accessible peripheral portion 75b that is notched, as is best seen in FIGS. 5 and 6, to permit insertion of the blade of a screw driver or other appropriate tool (not shown) for applying a tangential force thereto. In this manner the ring 75 can be rotated with respect to the body 77, thereby changing the angular location of the rings dependent part 75a which adjusts the deflection of the control spring 73 as desired.

While I have shown and described a preferred form of my invention by way of illustration, various modifications will undoubtedly occur to those skilled in the art. I contemplate therefore by the claims which conclude this specification to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electromagnetic induction relay:

(a) a magnetizable stator having a plurality of salient poles;

(b) a magnetizable extremities of said rality of gaps;

(c) a current-conducting element disposed for movement through said gaps;

(d) a plurality of magnetic flux producing coils on said stator, said coils when energized establishing in said gaps magnetic fields which interact in said element to produce a driving force therein;

(e) movable circuit controlling means coupled to said element and normally resting in a predetermined position from which it can be driven, upon operation of the relay, by said element moving in a given direc' tion;

(f) spring means connected to said circuit controlling means for yieldingly opposing movement thereof away from said predetermined position; and

(g) adjustment means having first, second, and third parts for controlling the stress on said spring means when said circuit controlling means is in its predetermined position,

member spaced apart from the poles to define therewith a plu- (i) said'first part comprising a'rotatable ring connected to said spring means and having a peripheral portion that is externally accessible,

(ii) said second part comprising a spring washer adjacent to said ring, and

(iii) said third part comprising a stationary supporting body adjacent to said spring washer, said body having a plurality of rigid fingers extended through and bent back over said ring so as to capture said washer and said ring between said fingers and said body, whereby the ring can be rotated to deflect said spring means by applying a tangential force to said peripheral portion of the ring.

2. In an electromagnetic induction relay:

(a) a supporting bracket;

(b) a magnetizable stator mounted on said bracket, said stator including four inwardly projecting salient poles;

(c) a magnetizable core having an axis;

((1) means for mounting said core on said bracket in spaced relation to the extremities of said poles to define therewith a plurality of gaps;

(e) an electroconductive rotor pivotally supported in coaxial relation to said core for rotation through said (f) a plurality of magnetic flux producing coils on said stator, said coils when energized establishing in said gaps magnetic fields which interact in said rotor to produce a driving torque therein;

(g) a movable switch arm coupled to said rotor for actuation thereby;

(h) means including a spiral spring having one end connected to said arm for biasing said arm to a predetermined normal position, said spring being disposed coaxially with respect to said rotor; and

(j) adjustment means connected to said spring for controlling the amount that the spring is stressed, said adjustment means comprising (i) an annular body attached to said bracket in coaxial relation to said spring, said body having a plurality of bent-over fingers extending therefrom,

(ii) a spring washer, and

(iii) a rotatable ring disposed adjacent to said washer between said annular body and its fingers, said ring being connected to the other end of said spiral spring and having a peripheral portion that is externally accessible, whereby the ring can be rotated to adjust the deflection of said other end of said spring by applying a tangential force to its peripheral portion.

3. The relay of claim 2 in which at least one peripheral portion of said core is relatively flat and in which said means for mounting the core on said bracket comprises:

(i) a member secured to said core and extending axially therefrom through a cooperating opening in said bracket,

(ii) a rotatable element disposed on the opposite side of said bracket from said core and connected to said member for joint rotation therewith about said axis, said element having an externally accessible peripheral portion, and

(iii) means associated with said member for resiliently clamping together said element and said bracket, said element being rotatable by the application of a tangential force to its peripheral portion to adjust the angular position of said flat portion of said core.

4. In an electromagnetic relay:

(a) a rigid supporting member;

(b) a magnetizable stator mounted on said member, said stator including a plurality of inwardly projecting salient poles;

(c) a generally cylindrical magnetizable core having an axis, at least one portion of the periphery of said core being relatively flat;

(d) means for mounting said core on said member in spaced relation to the faces of said salient poles, whereby a plurality of generally symmetrical gaps are formed between said core and the respective pole faces, said mounting means comprising (i) a rotatable element keyed to said core for joint rotation with said core about said axis and having an externally accessible peripheral portion,

(ii) resilient means disposed between said element and said supporting member, and

(iii) means for firmly clamping said element against said spring means, whereby the element can be rotated to change the angular position of said core by applying an external force to its peripheral portion;

(e) a circuit control-ling electroconductive armature supported for rotation about the axis of said core and having a portion disposed in said gaps in overlapping relation with said pole faces; and

(f) a plurality of magnetic flux producing coils on said stator, said coils when energized establishing in said gaps magnetic fields which interact in said armature to produce a driving torque therein.

5. The relay of claim 4 in which said means for mounting said core on said supporting member includes a bushing secured to said core and extending axially therefrom through a cooperating opening in said member, said rotatable element is keyed to said bushing on the opposite side of said member from said core, and said clamping means comprises a nut threaded on the axial extension of said bushing.

6. In an electromagnetic induction relay:

(a) a supporting bracket;

(b) a magnetizable stator mounted on said bracket, said stator including four inwardly projecting salient poles;

(c) a generally cylindrical magnetizable core having an axis, at least one peripheral portion of said core being relatively flat;

(d) means for rotatably mounting said core on said bracket in spaced relation to the extremities of said poles to define therewith a plurality of gaps, said mounting means comprising a spring washer disposed between an appendage of said core and said bracket in coaxial relationship with said core and means for axially clamping together said washer, said appendage, and said bracket;

(e) an adjusting element keyed to said core for joint rotation therewith about said axis, said element having an externally accessible peripheral portion to which a tangential force can be applied for the purpose of adjusting the angular position of said flat portion of said core;

(f) a circuit-controlling electroconductive rotor pivotally supported in coaxial relation to said core for rotation through said gaps; and

(g) a plurality of magnetic flux producing coils on said stator, said coils when energized establishing in said gaps magnetic fields which interact in said rotor to produce a driving torque therein.

The Mho Distance Relay, R. M. Hutchinson, AIEE Transactions, vol. 65, June 1946, pages 353-56.

BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, JR., Assistant Exziminer. 

1. IN AN ELECTROMAGNETIC INDUCTION RELAY: (A) A MAGNETIZABLE STATOR HAVING A PLURALITY OF SALIENT POLES; (B) A MAGNETIZABLE MEMBER SPACED APART FROM THE EXTREMITIES OF SAID POLES TO DEFINE THEREWITH A PLURALITY OF GAPS; (C) A CURRENT-CONDUCTING ELEMENT DISPOSED FOR MOVEMENT THROUGH SAID GAPS; (D) A PLURALITY OF MAGNETIC FLUX PRODUCING COILS ON SAID STATOR, SAID COILS WHEN ENERGIZED ESTABLISHING IN SAID GAPS MAGNETIC FIELDS WHICH INTERACT IN SAID ELEMENT TO PRODUCE A DRIVING FORCE THEREIN; (E) MOVABLE CIRCUIT CONTROLLING MEANS COUPLED TO SAID ELEMENT AND NORMALLY RESTING IN A PREDETERMINED POSITION FROM WHICH IT CAN BE DRIVEN, UPON OPERATION OF THE RELAY; BY SAID ELEMENT MOVING IN A GIVEN DIRECTION; (F) SPRING MEANS CONNECTED TO SAID CIRCUIT CONTROLLING MEANS FOR YIELDINGLY OPPOSING MOVEMENT THEREOF AWAY FROM SAID PREDETERMINED POSITION; AND (G) ADJUSTMENT MEANS HAVING FIRST, SECOND, AND THIRD PARTS FOR CONTROLLING THE STRESS ON SAID SPRING MEANS WHEN SAID CIRCUIT CONTROLLING MEANS IS IN ITS PREDETERMINED POSITION, 